There are situations, particularly on a battlefield, where it is desired to be able to identify the type of a distant vehicle which cannot be adequately seen due to low or no light or due to smoke and/or dust and cannot be adequately heard due to general noise. If the vehicle is an enemy tank or helicopter, for example, it is prudent to fire large shells or missiles to eliminate it. If, on the other hand, the vehicle is a jeep, it is not considered a serious threat and little or no action would be taken to eliminate that vehicle.
The human mind is outstanding at recognizing and categorizing sounds if the sounds can be isolated from others. The present invention makes use of this human trait.